The present invention relates to an apparatus which detects changes in the height of an axle of a front wheel and/or an axle of a rear wheel of a vehicle so as to control the lighting direction of a vehicle lamp in accordance with change in the attitude of the vehicle.
An apparatus (a so-called "automatic leveling apparatus") is known which performs automatic correction in such a manner that a predetermined lighting direction of lamps (headlights) provided for a vehicle is always maintained if the attitude of running of the vehicle is changed.
An automatic leveling apparatus has a structure that, for example, a vehicle-height sensor is provided for each of front wheels and rear wheels of a vehicle or either of the front wheels or the rear wheels the vehicle. The foregoing automatic leveling apparatus is arranged to cause the vehicle-height sensor to measure change in the pitch angle (or the pitching angle) of the vehicle to move reflecting mirrors in the headlights to cancel the foregoing change so as to control the lighting direction of the lamp or the height of the cut line of a light distribution pattern of the low beam. Thus, glare (light) caused from change in the attitude of the vehicle can be prevented.
The conventional apparatus is arranged to change the response of the control to correspond to the degree of acceleration of the vehicle. Thus, control is quickly performed when the acceleration is large and the control is slowly performed when the acceleration is small.
The velocity of change of the pitch angle of the vehicle is not changed to correspond to the degree of the acceleration. The foregoing velocity is changed in proportion to the change rate of the acceleration with respect to time. Therefore, if quick change in the acceleration occurs in a state in which the acceleration is slow, delay in the control takes place. If light which is more upward than a horizontal plane is unnecessary emitted as dazzling light, there is apprehension that glare occurs.